My experience is that a corrupt media file can crash Vegas until it is found and deleted. Finding it with Vegas, of course, becomes impossible once the crashing starts. I seem to have provoked a crash by starting Internet Explorer while capturing DV from a DV camcorder through the computer's processor onto a firewire hard disk. This gave me a dropped-frames prompt and then, crash. Problem is, I didn't know which DV-avi file it was. If you tried using "new copies" of the media the problem may be in the source media files--maybe.

So instead of Vegas, you can either open the files one by one in Windows Media Player (which will give a prompt that it can't play the suspect file when you reach it), or delete everything you've captured and start over. I did the latter since I had only started capturing the first few files. P.S. I was capturing with Scenalyzer Live, not Vidcap.

Don't know if this solves your issue but it's offered for what it's worth.